Insulating window units having at least two window panes, which are held apart from each other in the insulating window unit, are known. Insulating windows are normally formed from an inorganic or organic glass or from other materials like Plexiglas. Normally, the separation of the window panes is secured by a spacer frame (see reference number 50 in FIG. 1). The spacer frame is either assembled from several pieces using connectors or is bent from one piece (see FIG. 2), so that then the spacer frame 50 is closable by a connector 54 at only one position.
Various designs have been utilized for insulating window units that are intended to provide good heat insulation. According to one design, the intervening space between the panes is preferably filled with inert, insulating gas, e.g., such as argon, krypton, xenon, etc. Naturally, this filling gas should not be permitted leak out of the intervening space between the panes. Consequently, the intervening space between the panes must be sealed accordingly. Moreover, nitrogen, oxygen, water, etc., contained in the ambient air naturally also should not be permitted enter into the intervening space between the panes. Therefore, the spacer profile must be designed so as to prevent such diffusion. In the description below, when the term “diffusion impermeability” is utilized with respect to the spacer profiles and/or the materials forming the spacer profile, vapor diffusion impermeability, as well as also gas diffusion impermeability for the gases relevant herein, are meant to be encompassed within the meaning thereof.
Furthermore, the heat transmission of the edge connection, i.e. the connection of the frame of the insulating window unit, of the window panes, and of the spacer frame, in particular, plays a very large role for achieving low heat conduction of these insulating window units. Insulating window units, which ensure high heat insulation along the edge connection, fulfill “warm edge” conditions as this term is utilized in the art.
Conventionally, spacer profiles were manufactured from metal. Such metal spacer profiles can not, however, fulfill “warm edge” conditions. Thus, in order to improve upon such metal spacer profiles, the provision of synthetic material on the metal spacer profile has been described, e.g., in U.S. Pat. No. 4,222,213 or DE 102 26 268 A1.
Although a spacer, which exclusively consists of a synthetic material having a low heat conduction value, could be expected to fulfill the “warm edge” conditions, the requirements of diffusion impermeability and strength would be very difficult to satisfy.
Other known solutions include spacer profiles made of synthetic material that are provided with a metal film as a diffusion barrier and reinforcement layer, as shown, e.g., in EP 0 953 715 A2 (family member U.S. Pat. No. 6,192,652) or EP 1 017 923 (family member U.S. Pat. No. 6,339,909).
Such composite spacer profiles use a profile body made of synthetic material with a metal film, which should be as thin as possible in order to satisfy the “warm edge” conditions, but should have a certain minimum thickness in order to guarantee diffusion impermeability and strength.
Because metal is a substantially better heat conductor than synthetic material, it has been attempted, e.g., to design the heat conduction path between the side edges/walls of the spacer profile (i.e. through or via the metal film) to be as long as possible (see EP 1 017 923 A1).
For improved gas impermeability, the spacer frame is preferably bent from a one-piece spacer profile, if possible by cold bending (at a room temperature of approximately 20° C.), whereby only one position that potentially impairs the gas impermeability is provided, i.e. the gap between the respective ends of the bent spacer frame. A connector is affixed to the bent spacer frame in order to close and seal this gap.
When the spacer profile is bent, in particular when cold bending techniques are used, there is a problem of wrinkle formation at the bends (see FIG. 3c). The advantage of cold bending is, as was already mentioned above, that superior diffusion impermeability and increased durability of the insulating window unit result.
According to the solution known from EP 1 017 923 A1, the problem of wrinkle formation has been well solved, but the space available in the chamber for the desiccating material is not satisfactory, in particular for small distances between panes, i.e. separation distances less than 12 mm, and more particularly for separation distances of 6, 8 or 10 mm. According to other solutions, such as those shown, e.g., in FIG. 1 of EP 0 953 715 A2, the problem of wrinkle formation in the bends, in particular, still remains. Moreover, according to both solutions, when the spacer profile is intended to be utilized in a large frame, the problem of considerable sag along unsupported, lengthy portions of the spacer profile exists (see FIGS. 3a and 3b).
A composite spacer profile is also known from EP 0 601 488 A2 (family member U.S. Pat. No. 5,460,862), wherein a stiffening support is embedded on the side of the profile that faces toward the intervening space between the panes in the assembled state.